As is well known, upon color development of a silver halide color photographic material, an oxidized aromatic primary amine color developing agent reacts with a coupler to form a dye such as indophenol, indoaniline, indamine, azomethine, phenoxanine, and phenazine, thereby producing a dye image. In this system, the subtractive color process is employed for color reproduction; silver halide emulsions selectively sensitive to blue, green and red, and color image forming agents in a complementary color relation of yellow, magenta and cyan, respectively, are used. An acylacetanilide- or dibenzoylmethane-based coupler, for example, is used to form a yellow color image; a pyrazolone-, pyrazolobenzimidazole-, cyanoacetophenone-, or indazolone-based coupler is generally used to form a magenta color image; and a phenol-based coupler (e.g., phenols and naphthols) is generally used to form a cyan color image.
In recent years, with the use of disc cameras and 110 format cameras, it has been increasingly desired to increase the quality of a silver halide photographic material, particularly a color photographic material. In particular, the improvement of sharpness and graininess is important.
It is known to use a coupler not only to form a dye image, but also to release a photographically useful group. Such compounds releasing a photographically useful group are used for various purposes such as improvement of graininess, increase of sharpness, and increase of sensitivity.
A new coupler has been proposed in which a compound capable of capturing an oxidized color developing agent is linked to the coupling position of the coupler. Such couplers are used to trap imagewise the oxidized color developing agent formed according to an exposure amount so that the graininess and gradation of the image can be controlled without deterioration of sensitivity. Typical examples of the couplers are (1) couplers as described in Japanese Patent Application (OPI) Nos. 150631/77 (corresponding to U.S. Pat. No. 4,130,427) and 111537/82 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") in which a white coupler, or a diffusion type coupler forming a dye capable of flowing out from the photographic material is linked in the coupling position, and (2) couplers as described in Japanese Patent Application (OPI) No. 138636/82 which are substituted with a compound capable of cross oxidation with an oxidized color developing agent and of reducing the oxidized product into the color developing agent, in the coupling position thereof.
Although the above compounds have proved effective in controlling the graininess and gradation of dye images, they have several disadvantages. One of the disadvantages is that a reduction in sensitivity is observed. Another disadvantage is that the effect of controlling the graininess and gradation is generally poor and, furthermore, unlike known DIR couplers they cannot improve sharpness. Still another disadvantage is that they are not expected to increase color reproductivity by exerting an interlayer effect on other layers and, in fact, they do not have this effect. This is believed to be due to the fact that the diffusibility of the compound per se, which is capable of capturing the oxidized color developing agent released from the coupler, is small.